Locating the s, p, d, and f Blocks on the Periodic Table

Hello again. In the previous lesson, you learned that a period is a horizontal row and that its number tells you the outermost occupied electron shell. You also distinguished the outer valence electrons from inner electrons.

Now we add a second map feature: the periodic table is divided into four large regions called the s, p, d, and f blocks. You do not need to write complicated electron configurations yet. Your goal is to look at any normal periodic table and quickly point to each block.

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Why are there “blocks”?

Electrons occupy shells, but each shell has smaller sections called subshells. The subshell types are named s, p, d, and f.

The periodic table’s shape is not random. Its four differently sized regions reflect those four subshell types:

Block	Width	What to notice
s block	2 columns	The narrow region on the left
p block	6 columns	The region on the right
d block	10 columns	The broad central region
f block	14 columns	The two detached rows at the bottom

The letters are lowercase: s, p, d, f. For this lesson, treat them as labels for four regions of the table. Later, you will use the blocks to make sense of electron arrangements and recurring chemical patterns.

Watch this short segment from Khan Academy’s Electron Configurations with the Periodic Table. It connects the periods and groups you already know with the four blocks.

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See the four regions as one shape

Use the colored table below as your main visual reference. Each color is one block.

A reliable way to orient yourself is to read the table in four visual pieces:

1. The left edge is the s block.
2. The right edge is the p block.
3. The middle bridge is the d block.
4. The two rows below are the f block.

Notice that the table has a large gap between the left and right sides in periods 2 and 3. That is because the d block does not begin until period 4. The f block does not begin until periods 6 and 7.

The image’s colors are only a learning aid. Other periodic tables may use different colors, or no colors at all, so learn the position and width of each region rather than depending on color.

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The s block: the two left-hand columns

The s block occupies the first two columns on the far left of the table:

• Group 1 is the first s-block column.
• Group 2 is the second s-block column.

Examples include:

• Hydrogen, $\mathrm{H}$, at the top left
• Lithium, $\mathrm{Li}$
• Sodium, $\mathrm{Na}$
• Beryllium, $\mathrm{Be}$
• Magnesium, $\mathrm{Mg}$

A useful memory cue is:

s = start of the table.

That is not what the letter s scientifically means, but it is a helpful location mnemonic: the s block starts the row.

The helium exception

Helium, $\mathrm{He}$, is an important exception in its placement. It appears at the top right with the noble gases because its chemical behavior resembles theirs. However, its electron arrangement ends in an s subshell, so helium belongs to the s block in electron-configuration terms.

So remember both facts:

• Location on the printed table: top right.
• Block identity: s block.

This exception is worth learning now so it does not surprise you later.

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The p block: the six right-hand columns

The p block is the six-column region on the far right. It covers groups 13 through 18, except that helium is not a p-block element despite being placed above group 18.

For the first three periods, you have already met several p-block elements:

Element	Symbol	Position within p block
Boron	$\mathrm{B}$	First p-block column
Carbon	$\mathrm{C}$	Second p-block column
Nitrogen	$\mathrm{N}$	Third p-block column
Oxygen	$\mathrm{O}$	Fourth p-block column
Fluorine	$\mathrm{F}$	Fifth p-block column
Neon	$\mathrm{Ne}$	Sixth p-block column
Aluminium	$\mathrm{Al}$	First p-block column of period 3
Chlorine	$\mathrm{Cl}$	Fifth p-block column of period 3
Argon	$\mathrm{Ar}$	Sixth p-block column of period 3

The p block is easy to recognize because it forms the table’s right-hand rectangle, beginning with boron in period 2. The top-right position is occupied by helium, but the rest of the p block begins one row lower.

A memory cue:

p = the piece on the right.

Again, this is only a location mnemonic, not the scientific origin of the letter.

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The d block: the ten-column middle

The d block is the wide, ten-column region in the center of the periodic table. It spans groups 3 through 12.

It first appears in period 4, beginning with scandium, $\mathrm{Sc}$, and ending with zinc, $\mathrm{Zn}$. In the colored image, it is the blue band between the green s block and purple p block.

Many d-block elements are called transition metals. You will study their properties later; for now, connect the label to its location:

The d block is the central region that transitions from the left-side s block to the right-side p block.

Examples from the first d-block row include:

• Scandium, $\mathrm{Sc}$
• Titanium, $\mathrm{Ti}$
• Iron, $\mathrm{Fe}$
• Copper, $\mathrm{Cu}$
• Zinc, $\mathrm{Zn}$

The d block has ten columns, which helps distinguish it from every other block. It is wider than the s and p blocks, but narrower than the f block.

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The f block: the two detached bottom rows

The f block is displayed as the two long rows below the main body of the table. Each row contains 14 positions.

• The upper detached row is associated with period 6 and is called the lanthanide series.
• The lower detached row is associated with period 7 and is called the actinide series.

For example:

• Cerium, $\mathrm{Ce}$, is in the upper f-block row.
• Uranium, $\mathrm{U}$, is in the lower f-block row.

These rows are not truly separate from the rest of the table. They are placed underneath to keep the table compact enough to fit on a page. In a full-width version, they fit into periods 6 and 7 between the left-hand s block and central d block.

A useful memory cue:

f = the floor of the table.

The f block sits “on the floor,” below the main table.

Read the short LibreTexts explanation to reinforce why the regions have widths of 2, 6, 10, and 14.

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A quick identification routine

When you are handed an unfamiliar periodic table, use this routine:

If you see...	You have found...
The first two columns at the far left	s block
Six columns at the far right	p block
Ten columns in the middle, beginning in period 4	d block
Two detached 14-element rows beneath the table	f block

Then make one correction:

• If you are classifying blocks by electron configuration, helium is s block, even though it is drawn at the top right.

You can also identify an element’s block just by locating its square:

Element	Where it sits	Block
Magnesium, $\mathrm{Mg}$	Left, second column	s block
Oxygen, $\mathrm{O}$	Right-hand region	p block
Iron, $\mathrm{Fe}$	Central region	d block
Neodymium, $\mathrm{Nd}$	Upper detached row	f block
Uranium, $\mathrm{U}$	Lower detached row	f block
Helium, $\mathrm{He}$	Top right, but exceptional	s block

For a short memory practice, cover the block labels on the colored image. Point to each region and say: “s: left two; p: right six; d: middle ten; f: bottom fourteen.” Then uncover the labels and check yourself. Repeating that visual recall on a few separate days will make the layout much more durable than rereading it once.

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Key takeaways

• The periodic table has four electron-configuration regions: s, p, d, and f blocks.
• The s block is the two-column region on the left.
• The p block is the six-column region on the right.
• The d block is the ten-column region in the middle, beginning in period 4.
• The f block is the pair of detached 14-element rows at the bottom.
• Helium is placed with the noble gases at the top right, but it is an s-block element.
• A compact recall phrase is: left two, right six, middle ten, bottom fourteen.

Next, you will return to memorization practice and extend your element knowledge beyond the first 18 elements, using the table’s structure as a guide rather than treating it as a random list.